upstream: Allow some keywords to expand shell-style ${ENV}

environment variables on the client side.  The supported keywords are
CertificateFile, ControlPath, IdentityAgent and IdentityFile, plus
LocalForward and RemoteForward when used for Unix domain socket paths.  This
would for example allow forwarding of Unix domain socket paths that change at
runtime.  bz#3140, ok djm@

OpenBSD-Commit-ID: a4a2e801fc2d4df2fe0e58f50d9c81b03822dffa

1 files changed, 43 insertions, 10 deletions

diff --git a/ssh_config.5 b/ssh_config.5
index dc010ccbd..001544dd3 100644
--- a/ssh_config.5
+++ b/ssh_config.5
@@ -33,8 +33,8 @@
 .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 .\"
-.\" $OpenBSD: ssh_config.5,v 1.325 2020/04/11 20:20:09 jmc Exp $
-.Dd $Mdocdate: April 11 2020 $
+.\" $OpenBSD: ssh_config.5,v 1.326 2020/05/29 04:25:40 dtucker Exp $
+.Dd $Mdocdate: May 29 2020 $
 .Dt SSH_CONFIG 5
 .Os
 .Sh NAME
@@ -389,9 +389,11 @@ or
 .Pp
 Arguments to
 .Cm CertificateFile
-may use the tilde syntax to refer to a user's home directory
-or the tokens described in the
+may use the tilde syntax to refer to a user's home directory,
+the tokens described in the
 .Sx TOKENS
+section and environment variables as described in the
+.Sx ENVIRONMENT VARIABLES
 section.
 .Pp
 It is possible to have multiple certificate files specified in
@@ -551,9 +553,11 @@ section above or the string
 to disable connection sharing.
 Arguments to
 .Cm ControlPath
-may use the tilde syntax to refer to a user's home directory
-or the tokens described in the
+may use the tilde syntax to refer to a user's home directory,
+the tokens described in the
 .Sx TOKENS
+section and environment variables as described in the
+.Sx ENVIRONMENT VARIABLES
 section.
 It is recommended that any
 .Cm ControlPath
@@ -934,9 +938,11 @@ the location of the socket.
 .Pp
 Arguments to
 .Cm IdentityAgent
-may use the tilde syntax to refer to a user's home directory
-or the tokens described in the
+may use the tilde syntax to refer to a user's home directory,
+the tokens described in the
 .Sx TOKENS
+section and environment variables as described in the
+.Sx ENVIRONMENT VARIABLES
 section.
 .It Cm IdentityFile
 Specifies a file from which the user's DSA, ECDSA, authenticator-hosted ECDSA,
@@ -1152,8 +1158,10 @@ indicates that the listening port be bound for local use only, while an
 empty address or
 .Sq *
 indicates that the port should be available from all interfaces.
-Unix domain socket paths accept the tokens described in the
+Unix domain socket paths may use the tokens described in the
 .Sx TOKENS
+section and environment variables as described in the
+.Sx ENVIRONMENT VARIABLES
 section.
 .It Cm LogLevel
 Gives the verbosity level that is used when logging messages from
@@ -1423,8 +1431,10 @@ Multiple forwardings may be specified, and additional
 forwardings can be given on the command line.
 Privileged ports can be forwarded only when
 logging in as root on the remote machine.
-Unix domain socket paths accept the tokens described in the
+Unix domain socket paths may use the tokens described in the
 .Sx TOKENS
+section and environment variables as described in the
+.Sx ENVIRONMENT VARIABLES
 section.
 .Pp
 If the
@@ -1875,6 +1885,29 @@ accepts all tokens.
 .Pp
 .Cm ProxyCommand
 accepts the tokens %%, %h, %n, %p, and %r.
+.Sh ENVIRONMENT VARIABLES
+Arguments to some keywords can be expanded at runtime from environment
+variables on the client by enclosing them in
+.Ic ${} ,
+for example
+.Ic ${HOME}/.ssh
+would refer to the user's .ssh directory.
+If a specified environment variable does not exist then an error will be
+returned and the setting for that keyword will be ignored.
+.Pp
+The keywords
+.El
+.Cm CertificateFile ,
+.Cm ControlPath ,
+.Cm IdentityAgent
+and
+.Cm IdentityFile
+support environment variables.
+The keywords
+.Cm LocalForward
+and
+.Cm RemoteForward
+support environment variables only for Unix domain socket paths.
 .Sh FILES
 .Bl -tag -width Ds
 .It Pa ~/.ssh/config